Multi input Multi output (MIMO) technology in mobile network requires a Remote Radio Unit (RRU), which transmits and receives simultaneously many signal channels. So, the size of RRU must be minimized. This paper is concerned to minimize the size of cavity resonator by changing the cavity shape. A hexagonal cavity resonator is used to decrease the area of duplexer which ensures all required characteristics. A duplexer with eleven hexagon cavity resonators which operates at Band 3 is synthesized, designed and optimizedby CST software. The simulation results archives all required characteristics, the area of duplexer can be reduced approximately to 10% as the rectangular cavity with the same topology. After designing, the final 3D model is built in AutoCad software and is fabricated. The measurement results are in a very good agreement with the simulation results.

LTE-A, hexagon, duplexer, cavity resonator.